Unify UME World as hex nav with conditional flat world map.

Seed a unique L2 World canvas under the UME World container, show the flat map only when nested regions have NEs, pack blocks without overlap, allow drag overrides on the world map while forbidding direct NE adds, and hide the world-map truncation banner.

Co-authored-by: Cursor <cursoragent@cursor.com>

web/src/i18n/en.ts

@@ -1423,6 +1423,12 @@ const en = {
     newRegion: "New region",
     newRegionName: "New region",
     newRegionPrompt: "Region name",
+    newSubRegion: "New sub-region",
+    newSubRegionName: "New sub-region",
+    newSubRegionPrompt: "Sub-region name",
+    subRegionNotOnFlat: "The flat world map has no regions. Create sub-regions on World or a lower-level canvas.",
+    worldMapNoDirectNes: "Cannot add NEs on the world map — add them on a sub-region canvas.",
+    subRegionNeedParent: "Open a region canvas first, then create a sub-region.",
     regionCreated: "Region created",
     regionDeleted: "Region deleted",
     deleteRegion: "Delete region",

web/src/i18n/zh.ts

@@ -1414,6 +1414,12 @@ const zh = {
     newRegion: "新建区域",
     newRegionName: "新区域",
     newRegionPrompt: "区域名称",
+    newSubRegion: "新建子区域",
+    newSubRegionName: "新子区域",
+    newSubRegionPrompt: "子区域名称",
+    subRegionNotOnFlat: "完整世界地图不支持子区域，请在 World 或下级区域画布上创建。",
+    worldMapNoDirectNes: "世界地图不能直接添加网元，请到某个子区域画布上添加。",
+    subRegionNeedParent: "请先打开一个区域画布，再新建子区域。",
     regionCreated: "区域已创建",
     regionDeleted: "区域已删除",
     deleteRegion: "删除区域",